Plasma shallow doping and wet removal of depth control cap

ABSTRACT

A gas is ionized into a plasma. A compound of a dopant is mixed into the plasma, forming a mixed plasma. Using a semiconductor device fabrication system, a layer of III-V material is exposed to the mixed plasma to dope the layer with the dopant up to a depth in the layer, forming a shallow doped portion of the layer. The depth of the dopant is controlled by a second layer of the dopant formed at the shallow doped portion of the layer. The second layer is exposed to a solution, where the solution is prepared to erode the dopant in the second layer at a first rate. After an elapsed period, the solution is removed from the second layer, wherein the elapsed period is insufficient to erode a total depth of the layer and the shallow doped portion by more than a tolerance erosion amount.

TECHNICAL FIELD

The present invention relates generally to a method, system, andcomputer program product for implanting dopants in semiconductorfabrication. More particularly, the present invention relates to amethod, system, and computer program product for plasma shallow dopingand wet removal of depth control cap.

BACKGROUND

An integrated circuit (IC) is an electronic circuit formed using asemiconductor material, such as Silicon, as a substrate and by adding(doping) impurities (dopants) to form solid-state electronic devices,such as transistors, diodes, capacitors, and resistors. The softwaretools used for designing ICs produce, manipulate, or otherwise work withthe circuit layout and circuit components on very small scales. Some ofthe components that such a tool may manipulate may only measure a fewnanometer across when formed in Silicon. The designs produced andmanipulated using these software tools are complex, often includinghundreds of thousands of such components interconnected to form anintended electronic circuitry.

Once a design layout, also referred to simply as a layout, has beenfinalized for an IC, the design is converted into a set of masks orreticles. During manufacture, a semiconductor wafer is exposed toradiation through a mask to form microscopic components of the IC. Thisprocess is known as photolithography. During the photolithographicprinting process, radiation is focused through the mask and at certaindesired intensity of the radiation. This intensity of the radiation iscommonly referred to as “dose”. The focus and the dosing of theradiation has to be precisely controlled to achieve the desired shapeand electrical characteristics on the wafer.

Many semiconductor devices are planar, i.e., where the semiconductorstructures are fabricated on one plane. A non-planar device is athree-dimensional (3D) device where some of the structures are formedabove or below a given plane of fabrication. A fin-Field EffectTransistor (finFET) is an example of a non-planar device.

Doping can be performed on a plane of a planar device, or on multipleplanes of a non-planar device. Furthermore, an electricalcharacteristic, such as conductivity or resistivity of a layer,semiconducting behavior of a channel, and the like, are controllablethrough the type of dopant used for doping, a concentration of thedopant, and a depth to which the dopant is implanted into a given layer.

SUMMARY

The illustrative embodiments provide a method, system, and computerprogram product. An embodiment includes a method that ionizes a gas intoa plasma. The embodiment mixes a compound of a dopant into the plasma,forming a mixed plasma. The embodiment exposes, using a semiconductordevice fabrication system, a layer of III-V material to the mixed plasmato dope the layer with the dopant up to a depth in the layer, forming ashallow doped portion of the layer. The embodiment controls the depth ofthe dopant by a second layer of the dopant formed at the shallow dopedportion of the layer. The embodiment exposes the second layer to asolution, the solution prepared to erode the dopant in the second layerat a first rate. The embodiment removes, after an elapsed period, thesolution from the second layer, wherein the elapsed period isinsufficient to erode a total depth of the layer and the shallow dopedportion by more than a tolerance erosion amount.

An embodiment includes a computer usable program product. The computerusable program product includes one or more computer-readable storagedevices, and program instructions stored on at least one of the one ormore storage devices.

An embodiment includes a computer system. The computer system includesone or more processors, one or more computer-readable memories, and oneor more computer-readable storage devices, and program instructionsstored on at least one of the one or more storage devices for executionby at least one of the one or more processors via at least one of theone or more memories.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the invention are setforth in the appended claims. The invention itself, however, as well asa preferred mode of use, further objectives and advantages thereof, willbest be understood by reference to the following detailed description ofthe illustrative embodiments when read in conjunction with theaccompanying drawings, wherein:

FIG. 1 depicts a block diagram of a network of data processing systemsin which illustrative embodiments may be implemented;

FIG. 2 depicts a block diagram of a data processing system in whichillustrative embodiments may be implemented;

FIG. 3 depicts a block diagram of an example semiconductor deviceconfiguration in which a layer has to be shallow doped in accordancewith an illustrative embodiment;

FIG. 4 depicts the example removal of oxygen from the native oxidemolecules in accordance with an illustrative embodiment;

FIG. 5 depicts an example shallow doping process in accordance with anillustrative embodiment;

FIG. 6 depicts a depositing of a capping material to control the dopingdepth in accordance with an illustrative embodiment;

FIG. 7 depicts a graph of III-V material loss using a wet removalprocess in accordance with an illustrative embodiment;

FIG. 8 depicts measurement plots of Si cap thickness reduction through awet removal process in accordance with an illustrative embodiment;

FIG. 9 depicts a flowchart of an example process for in-situ shallowplasma doping in accordance with an illustrative embodiment; and

FIG. 10 depicts a flowchart of a wet removal process in accordance withan illustrative embodiment.

DETAILED DESCRIPTION

The illustrative embodiments recognize that controlling doping depth isa difficult problem in semiconductor fabrication. As a non-limitingexample, a III-V material layer, such as Indium-Gallium-Arsenide(InGaAs), has to be doped with Silicon (Si) or Germanium (Ge) in manycircumstances.

For example, electron mobility may have to be improved in a InGaAschannel, for which shallow Si doping is needed. To give somenon-limiting examples, the InGaAs layer may be ten nanometer (nm) to onehundred nm or more deep. Accordingly, shallow doping would reach fromlow single digit nm depth to few tens of nm depth into the InGaAs layer,e.g., one-to-five nm to ten-to-thirty nm depth, respectively. Shallowdoping is also known as surface doping.

The illustrative embodiments recognize that if Si is implanted too deepinto the InGaAs channel, then the InGaAs and Si become diffused into oneanother, reducing electron mobility. Many other III-V materials have tobe shallow implanted with Si or other similar dopants for these andother reasons.

The illustrative embodiments further recognize that controlling thedepth of the doping, and the doping process generally is hindered by theoxides that form on the III-V material layer. If the oxide is notremoved, the doping is at least not accomplished to a suitable depth,and can be ineffective at the worst.

Presently, Hydrochloric acid (HCl) or Hydrofluoric acid (HF) solution isused to remove oxidation in semiconductor fabrication. The illustrativeembodiments recognize that InGaAs native oxides are not removable withthis solution. If the native oxides are present on the surface wheredoping has to be applied, the surface doping is not effective.

The illustrative embodiments used to describe the invention generallyaddress and solve the above-described problems and other problemsrelated to shallow doping of III-V material layers. The illustrativeembodiments provide a method for plasma shallow doping and wet removalof depth control cap.

An embodiment can be implemented as a software application. Theapplication implementing an embodiment can be configured as amodification of an existing semiconductor fabrication system, as aseparate application that operates in conjunction with an existingsemiconductor fabrication system, a standalone application, or somecombination thereof. For example, the application causes thesemiconductor fabrication system to perform the steps described herein,to implant a dopant to a shallow depth and thereafter clean anystructures created for the shallow doping, as described herein.

For the clarity of the description, and without implying any limitationthereto, the illustrative embodiments are described using a InGaAs as anexample III-V material, Si as an example dopant, and Argon (Ar) as anexample material in an ionized form in a plasma as described herein. Anembodiment can be implemented with a different III-V materials—such asGallium Arsenide Indium Phosphide, different dopants—such as Germanium,different plasma—such as ionized Helium, or some combination of theseand other similarly purposed materials within the scope of theillustrative embodiments.

Furthermore, some compositions, dilutions, temperatures, durations,thicknesses, depths, and other measurements are described herein only asnon-limiting examples. Some of these described measurements have beenused in experimentations related to certain inventive aspects describedherein, and are usable in a preferred embodiment. However, theseexamples of measurements are not intended to be limiting. From thisdisclosure, those of ordinary skill in the art will be able to conceivemany other variations of the measurements, such as differentcompositions, dilutions, temperatures, durations, thicknesses, ordepths, to achieve similar or comparable results as an embodiment, andsuch variations are contemplated within the scope of the illustrativeembodiments.

Furthermore, a simplified diagram of an example transistor is used inthe figures and the illustrative embodiments. In an actual fabricationof a semiconductor device, such as a finFET, additional structures thatare not shown or described herein may be present, can be doped using anembodiment, or both, without departing the scope of the illustrativeembodiments. Similarly, within the scope of the illustrativeembodiments, a shown or described structure layer may be fabricated orimplemented differently to yield a similar operation or result asdescribed herein.

Differently shaded portions in the two-dimensional drawings are intendedto represent different materials unless expressly described differentlywhere used. The different materials may be replaced with other materialsthat are known to those of ordinary skill in the art as having a similarproperty as the described material.

A specific shape or dimension of a shape depicted herein is not intendedto be limiting on the illustrative embodiments. The shapes anddimensions are chosen only for the clarity of the drawings and thedescription and may have been exaggerated, minimized, or otherwisechanged from actual shapes and dimensions that might be used in anactual shallow doping operation according to the illustrativeembodiments.

Furthermore, the illustrative embodiments are described with respect toa transistor only as an example. The steps described by the variousillustrative embodiments can be adapted for fabricating other planar andnon-planar devices in a similar manner, and such adaptations arecontemplated within the scope of the illustrative embodiments. Those ofordinary skill in the art will be able to use an embodiment to controlthe depth of doping in the fabrication of any device and in any plane ofthe device, and such usage is also contemplated within the scope of theillustrative embodiments.

An embodiment when implemented in an application causes a fabricationprocess to performs certain steps as described herein. The steps of thefabrication process are depicted in the several figures. Not all stepsmay be necessary in a particular fabrication process. Some fabricationprocesses may implement the steps in different order, combine certainsteps, remove or replace certain steps, or perform some combination ofthese and other manipulations of steps, without departing the scope ofthe illustrative embodiments.

The manner of plasma shallow doping and wet removal of depth control capdescribed herein is unavailable in the presently available methods. Amethod of an embodiment described herein, when implemented to execute ona device or data processing system, comprises substantial advancement ofthe functionality of that device or data processing system infabricating semiconductor devices where the depth of implanting a dopantinto a III-V material layer has to be controlled.

The illustrative embodiments are described with respect to certain typesof devices, layers, planes, structures, materials, compositions,dilutions, temperatures, durations, thicknesses, depths, measurements,numerosity, data processing systems, environments, components, andapplications only as examples. Any specific manifestations of these andother similar artifacts are not intended to be limiting to theinvention. Any suitable manifestation of these and other similarartifacts can be selected within the scope of the illustrativeembodiments.

Furthermore, the illustrative embodiments may be implemented withrespect to any type of data, data source, or access to a data sourceover a data network. Any type of data storage device may provide thedata to an embodiment of the invention, either locally at a dataprocessing system or over a data network, within the scope of theinvention. Where an embodiment is described using a mobile device, anytype of data storage device suitable for use with the mobile device mayprovide the data to such embodiment, either locally at the mobile deviceor over a data network, within the scope of the illustrativeembodiments.

The illustrative embodiments are described using specific code, designs,architectures, protocols, layouts, schematics, and tools only asexamples and are not limiting to the illustrative embodiments.Furthermore, the illustrative embodiments are described in someinstances using particular software, tools, and data processingenvironments only as an example for the clarity of the description. Theillustrative embodiments may be used in conjunction with othercomparable or similarly purposed structures, systems, applications, orarchitectures. For example, other comparable mobile devices, structures,systems, applications, or architectures therefor, may be used inconjunction with such embodiment of the invention within the scope ofthe invention. An illustrative embodiment may be implemented inhardware, software, or a combination thereof.

The examples in this disclosure are used only for the clarity of thedescription and are not limiting to the illustrative embodiments.Additional data, operations, actions, tasks, activities, andmanipulations will be conceivable from this disclosure and the same arecontemplated within the scope of the illustrative embodiments.

Any advantages listed herein are only examples and are not intended tobe limiting to the illustrative embodiments. Additional or differentadvantages may be realized by specific illustrative embodiments.Furthermore, a particular illustrative embodiment may have some, all, ornone of the advantages listed above.

With reference to the figures and in particular with reference to FIGS.1 and 2, these figures are example diagrams of data processingenvironments in which illustrative embodiments may be implemented. FIGS.1 and 2 are only examples and are not intended to assert or imply anylimitation with regard to the environments in which differentembodiments may be implemented. A particular implementation may makemany modifications to the depicted environments based on the followingdescription.

FIG. 1 depicts a block diagram of a network of data processing systemsin which illustrative embodiments may be implemented. Data processingenvironment 100 is a network of computers in which the illustrativeembodiments may be implemented. Data processing environment 100 includesnetwork 102. Network 102 is the medium used to provide communicationslinks between various devices and computers connected together withindata processing environment 100. Network 102 may include connections,such as wire, wireless communication links, or fiber optic cables.

Clients or servers are only example roles of certain data processingsystems connected to network 102 and are not intended to exclude otherconfigurations or roles for these data processing systems. Server 104and server 106 couple to network 102 along with storage unit 108.Software applications may execute on any computer in data processingenvironment 100. Clients 110, 112, and 114 are also coupled to network102. A data processing system, such as server 104 or 106, or client 110,112, or 114 may contain data and may have software applications orsoftware tools executing thereon.

Device 132 is an example of a mobile computing device. For example,device 132 can take the form of a smartphone, a tablet computer, alaptop computer, client 110 in a stationary or a portable form, awearable computing device, or any other suitable device. Any softwareapplication described as executing in another data processing system inFIG. 1 can be configured to execute in device 132 in a similar manner.Any data or information stored or produced in another data processingsystem in FIG. 1 can be configured to be stored or produced in device132 in a similar manner.

Application 105 implements an embodiment described herein. Fabricationsystem 107 is any suitable system for fabricating a semiconductordevice. Application 105 provides instructions to system 107 for shallowdoping of a III-V material layer in a manner described herein.

With reference to FIG. 2, this figure depicts a block diagram of a dataprocessing system in which illustrative embodiments may be implemented.Data processing system 200 is an example of a computer, such as servers104 and 106, or clients 110, 112, and 114 in FIG. 1, or another type ofdevice in which computer usable program code or instructionsimplementing the processes may be located for the illustrativeembodiments.

Data processing system 200 is also representative of a data processingsystem or a configuration therein, such as data processing system 132 inFIG. 1 in which computer usable program code or instructionsimplementing the processes of the illustrative embodiments may belocated. Data processing system 200 is described as a computer only asan example, without being limited thereto. Implementations in the formof other devices, such as device 132 in FIG. 1, may modify dataprocessing system 200, such as by adding a touch interface, and eveneliminate certain depicted components from data processing system 200without departing from the general description of the operations andfunctions of data processing system 200 described herein.

In the depicted example, data processing system 200 employs memorycontroller hub (NB/MCH) 202 and input/output (I/O) controller hub(SB/ICH) 204. Processing unit 206, main memory 208, and graphicsprocessor 210 are coupled in the example manner shown in this figure.Local area network (LAN) adapter 212, audio adapter 216, keyboard andmouse adapter 220, modem 222, read only memory (ROM) 224, universalserial bus (USB) and other ports 232, and PCI/PCIe devices 234 arecoupled through bus 238. Hard disk drive (HDD) or solid-state drive(SSD) 226 and CD-ROM 230 are coupled through bus 240. A super I/O (SIO)device 236 may be coupled through bus 238.

Memories, such as main memory 208, ROM 224, or flash memory (not shown),are some examples of computer usable storage devices. Hard disk drive orsolid state drive 226, CD-ROM 230, and other similarly usable devicesare some examples of computer usable storage devices including acomputer usable storage medium.

Instructions for applications or programs, such as application 105 inFIG. 1, are located on storage devices, such as in the form of code 226Aon hard disk drive 226, and may be loaded into at least one of one ormore memories, such as main memory 208, for execution by processing unit206. The processes of the illustrative embodiments may be performed byprocessing unit 206 using computer implemented instructions, which maybe located in a memory, such as, for example, main memory 208, read onlymemory 224, or in one or more peripheral devices.

Furthermore, in one case, code 226A may be downloaded over network 201Afrom remote system 201B, where similar code 201C is stored on a storagedevice 201D. in another case, code 226A may be downloaded over network201A to remote system 201B, where downloaded code 201C is stored on astorage device 201D.

The hardware in FIGS. 1-2 may vary depending on the implementation.Other internal hardware or peripheral devices, such as flash memory,equivalent non-volatile memory, or optical disk drives and the like, maybe used in addition to or in place of the hardware depicted in FIGS.1-2. In addition, the processes of the illustrative embodiments may beapplied to a multiprocessor data processing system.

With reference to FIG. 3, this figure depicts a block diagram of anexample semiconductor device configuration in which a layer has to beshallow doped in accordance with an illustrative embodiment. Application105 in FIG. 1 interacts with fabrication system 107 to produce ormanipulate configuration 300 as described herein.

Configuration 300 depicts substrate 302, which may be formed usingIndium Phosphide (InP) or other suitable material. Layer 304 is a layerof an example III-V material, such as, but not limited to, InGaAs. Oxidelayer 306 comprises native oxides of the III-V material, such as theoxides that are more stable than In₂O or Ga₂O.

Structure 308 is an example gate structure, fabricated to create anexample source and an example drain in layer 304.

An embodiment causes a fabrication system, such as fabrication system107 in FIG. 1, to direct ionized plasma 310 at a portion of oxide 306.Generally, plasma 310 can be of any suitable material that is known toremove oxygen from the native oxide molecules in layer 306 and exposeIn− (In negative), Ga− (Ga negative), and/or As− (As negative) bonds inthe III-V material. Preferably, the material of plasma is ionized Argon(Ar+, Ar positive) or Helium (He+, He positive).

By removing the oxygen from the native oxides, plasma 310 cleans thesurface in which shallow doping is to be performed. FIG. 4 depicts theexample removal of oxygen from the native oxide molecules in accordancewith an illustrative embodiment.

FIG. 5 depicts an example shallow doping process in accordance with anillustrative embodiment. Assume that the example III-V material of layer304 is to be shallow doped with non-limiting example material Si. Anembodiment causes the fabrication system to add silicon in a suitableform to plasma 310 of FIG. 3, thus forming plasma 510. Preferably, toshallow dope layer 304 with Si dopant, the embodiment causes plasma 510to include Silane (SiH₄). Silane causes Si (512) to be incorporated intothe III-V material of layer 304, forming layer 504. Adding Si depositionincreases the radicals such as Si+, SiH2+, and/or SiH3+ in layer 504.Increased radicals in layer 504 cause the sheet resistivity (Rs) oflayer 504 to reduce substantially.

FIG. 6 depicts a depositing of a capping material to control the dopingdepth in accordance with an illustrative embodiment. Layer 504 is thesame as layer 504 in FIG. 5.

By continuing bombarding layer 504 with plasma 510—which includes theplasma material ions, as in plasma 310 of FIG. 3, as well a suitabledoping material compound, such as Silane as in FIG. 5, plasma 510 beginsto form a layer of the doping material over layer 504.

The depositing forms cap 614. If the doping is of Si, then cap 614 is anSi layer, or Si cap. Depending upon the implementation, the depositingof cap 614 can be achieved by adjusting a concentration of the materialused for the doping, e.g., the concentration or amount of Silane usedper unit of time, per unit of material of plasma 310, or both, in Sidoping. Cap 614 can also be of other material, such as of Ge, and can bedeposited using a suitable compound or form of that material in asimilar manner.

Layer 504 comprises two distinct portions, to wit, portions 504A and504B. Portion 504A is called an intermix, and includes molecules of boththe III-V material and the dopant. Portion 504B is in substantially thesame state as layer 304 in FIG. 3, and includes molecules of the III-Vmaterial only. Some negligible amount of dopant molecules can be presentin portion 504B without departing from the illustrative embodiments.

Depth “A” of portion 504A is significantly small relative to the totaldepth (A+B) of layer 504. For example, A is generally of the order ofone to thirty percent of (A+B), but can be varied within and outsidethis example range depending upon the electron mobility needed in aparticular implementation.

Plasma 510 continues to be directed at layer 504 during the formation,and for some period after cap 614 is formed. During the formation, aswell as once formed, cap 614 restricts, tunes, limits, or otherwisecontrols the depth reached into layer 504 by the dopant carried inplasma 510. In other words, without cap 614, plasma 510 would cause thedopant to reach a greater-than-desirable depth into layer 504. Anembodiment causes cap 614 to be deposited in order to control the depthof portion 504A.

Within the scope of the illustrative embodiments, and depending upon thespecific implementation, the speed of depositing cap 614, the height orthickness of cap 614, the sparsity or density of cap 614, or somecombination thereof is adjustable to limit the penetration of the dopantinto layer 504. For example, an amount of Silane added to plasma 510 canbe adjusted to adjust a speed of depositing cap 614. A duration ofexposure to plasma 510 can be adjusted to adjust the height of cap 614,a speed of movement of plasma 510 can be adjusted to adjust the densityof cap 614.

These examples adjustments in forming cap 614 and controlling depth A ofportion 504A are not intended to be limiting. From this disclosure,those of ordinary skill in the art will be able to conceive many otherdepositing adjustments and the corresponding depth controls, and thesame are contemplated within the scope of the illustrative embodiments.

Once cap 614 has served its function in controlling the depth of theshallow doping into the III-V material, cap 614 has served its purposeand has to be removed. The illustrative embodiments recognize thatremoving cap 614 is a difficult problem. During the shallow dopingprocess, a Si-rich cap, e.g., cap 614, is adjacent to a layer ofintermixed Si and III-V material, which is in turn adjacent to a layerof III-V material. The challenge is to remove the Si-rich layer whilenot removing the intermixed layer at all or with negligible removal ofthe intermixed layer.

An embodiment causes the fabrication system to prepare a dilutedsolution of Tetra Methyl Ammonium Hydroxide (TMAH). The dilution can bein the range of twenty to thirty percent of TMAH.

Experimentation has shown that the dilution of twenty-five percent TMAHproduces desirable cap erosion results. Therefore, according to apreferred embodiment, the dilution should be at twenty-five percent ofTMAH.

The illustrative embodiments also provide that temperature of thediluted TMAH also plays a role in the erosion process. Experimentationsupports that twenty-five percent TMAH at room temperature(approximately twenty-to-twenty-five degrees Celsius) according to anembodiment, when exposed to cap 614 for a period of approximately 120minutes according to the embodiment, eroded cap 614 without attacking oreroding the intermix portion 504A and the III-V material portion 504B.The time to erode or dissolve the cap material is significantly lessthat the total exposure time.

According to another embodiment, the same dilution of TMAH atfifty-to-sixty degrees Celsius eroded cap 614 in approximately the sameamount of time as did the solution at room temperature, and dissolvedthe III-V material in intermix portion 504A at the rate of approximatelyeighty-five one-hundredths (0.85) nm per minute in an exposure time ofapproximately fifteen minutes.

Thus, the illustrative embodiments recognize that the temperature of thediluted TMAH solution and the total exposure time for which the cap isexposed to the TMAH solution are related by an inverse relationshipfunction. Generally, as the temperature of the solution rises by oneamount, the exposure time required reduces by another amount. Theinverse relationship function at or close to sea level atmosphericpressure satisfies at least the two example data points at roomtemperature and fifty-to-sixty degrees, as described above. Within thescope of the illustrative embodiments, the function may be different fordifferent temperature bands, different atmospheric pressures, otherfactors, or some combination thereof.

Accordingly, an embodiment causes the fabrication process to use therapid solubility of cap material and slow solubility of the III-Vmaterial in a diluted TMAH solution to remove cap 614. This method ofremoving the cap material is referred to as a wet removal process. Theembodiment adjusts the exposure time in the wet removal processaccording to the inverse relationship function of the temperature of thesolution. Preferably, the embodiment causes the fabrication system toset the exposure time to no more than fifteen minutes for the solutiontemperature of fifty-to-sixty degrees of a twenty-five percent TMAHsolution.

As an additional advantage, but not necessary for an embodiment to bepracticed, the removal of cap 614 using the TMAH solution may alsosmoothen the physical rough texture created by the plasma doping inlayer portion 504.

With reference to FIG. 7, this figure depicts a graph of III-V materialloss using a wet removal process in accordance with an illustrativeembodiment. As an example, the wet removal process plotted in graph 700is applied to layer 504 in FIG. 5, which is formed by shallow doping Siinto InGaAs. Four example data points are plotted. As an example, atwenty-five percent solution of TMAH at sixty degrees Celsius is usedfor the exposure.

Data point A shows that at exposure time of zero minutes, the remainingthickness of the InGaAs material is approximately 1270 Angstroms. Datapoint B shows that at exposure time of fifteen minutes, the remainingthickness of the InGaAs material is still approximately 1270 Angstroms.Data point C shows that at exposure time of thirty minutes, theremaining thickness of the InGaAs material is approximately 1225Angstroms. Data point D shows that at exposure time of forty-fiveminutes, the remaining thickness of the InGaAs material is approximately1100 Angstroms.

At the dissolving rate of InGaAs as plotted in graph 700, the observeddissolving rate of Si was four-to-eight Angstroms/minute. Thus, theexperimentation supports a conclusion of an embodiment that a solutionof approximately twenty-five percent TMAH at sixty degrees Celsius, whenexposed to InGaAs for a period of approximately fifteen minutes willnegligibly erode InGaAs while substantially eroding Si of the cap.

With reference to FIG. 8, this figure depicts measurement plots of Sicap thickness reduction through a wet removal process in accordance withan illustrative embodiment. As an example, the wet removal processplotted in graph 802 is applied to layer 504 in FIG. 5, which is formedby shallow doping Si into InGaAs. At the onset of the wet removalprocess, Si thickness—which is monitored by measuring SiAs cluster ions,is measured as reaching up to 1285 angstroms where InGaAs layer begins(area A of graph 802).

Again, as an example, a twenty-five percent solution of TMAH at sixtydegrees Celsius is used for an exposure time of fifteen minutes. Area Bof graph 804 shows that Si has been effectively removed and 1278Angstroms of InGaAs thickness still remains. Graph 804 shows that thesolution at the temperature and exposure time has only erodedapproximately seven Angstroms of InGaAs material while effectivelyremoving all of the Si cap from the Si cap, e.g., from cap 614 in FIG.6.

With reference to FIG. 9, this figure depicts a flowchart of an exampleprocess for in-situ shallow plasma doping in accordance with anillustrative embodiment. Process 900 can be implemented in application105 in FIG. 1, to cause the structures similar to layer 504 and cap 614of FIG. 6 to form.

The application causes a fabrication system to bombard a III-V materiallayer with ionized Ar or He plasma (block 902). The application causes afabrication system to combine a suitable dopant, e.g., Si or Ge in asuitable form, with the ionized Ar/He of the plasma (block 904).

The application causes a fabrication system to cause the combined plasmato remove a native oxide from the III-V material layer while implantingthe dopant in to the III-V material layer (block 906). The applicationcauses a fabrication system to cause the dopant from the combined plasmato form a cap or a layer at the site of the shallow dopant implanting(block 908).

The application causes a fabrication system to cause the cap to controlthe depth of the plasma penetration, thereby controlling the depth ofthe dopant implanting into the III-V material layer (block 910). Theapplication either ends process 900 or exits at exit point “A” to enterprocess 1000 of FIG. 10 at the corresponding entry point “A”.

With reference to FIG. 10, this figure depicts a flowchart of a wetremoval process in accordance with an illustrative embodiment. Process1000 can be implemented in application 105 in FIG. 1, to remove thecapping layer as described with respect to FIGS. 7 and 8.

The application causes a fabrication system to expose the surface of thecap to a suitable concentration of TMAH (block 1002). At the time of theexposure, the application causes a fabrication system to ensure that thetemperature of the TMAH solution is set in an acceptable range (block1004). For example, depending upon the implementation, theimplementation may require restricting the exposure time to a certainperiod. By using the inverse relationship function that is applicable tothe implementation environment, the application causes a fabricationsystem to compute the temperature of the TMAH solution. Conversely, theapplication causes a fabrication system to set the temperature, e.g., toapproximately 60 degrees Celsius, and either sets the exposure time to15 minutes under circumstances similar to the experiment describedherein or computes a different period according to the environmentfactors of the particular implementation.

The application causes a fabrication system to allow the cap to remainexposed to the TMAH solution at the set temperature for the determinedexposure time (block 1006). Upon the elapse of the exposure time, theapplication causes a fabrication system to obtain a shallow doped III-Vmaterial layer without the cap (block 1008). The application endsprocess 1000 thereafter.

Thus, a computer implemented method, system or apparatus, and computerprogram product are provided in the illustrative embodiments for plasmashallow doping and wet removal of depth control cap and other relatedfeatures, functions, or operations.

Where an embodiment is described as implemented in an application, thedelivery of the application in a Software as a Service (SaaS) model iscontemplated within the scope of the illustrative embodiments. In a SaaSmodel, the capability of the application implementing an embodiment isprovided to a user by executing the application in a cloudinfrastructure. The user can access the application using a variety ofclient devices through a thin client interface such as a web browser(e.g., web-based e-mail), or other light-weight client-applications. Theuser does not manage or control the underlying cloud infrastructureincluding the network, servers, operating systems, or the storage of thecloud infrastructure. In some cases, the user may not even manage orcontrol the capabilities of the SaaS application. In some other cases,the SaaS implementation of the application may permit a possibleexception of limited user-specific application configuration settings.

The present invention may be a system, a method, and/or a computerprogram product at any possible technical detail level of integration.The computer program product may include a computer readable storagemedium (or media) having computer readable program instructions thereonfor causing a processor to carry out aspects of the present invention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, configuration data for integrated circuitry, oreither source code or object code written in any combination of one ormore programming languages, including an object oriented programminglanguage such as Smalltalk, C++, or the like, and procedural programminglanguages, such as the “C” programming language or similar programminglanguages. The computer readable program instructions may executeentirely on the user's computer, partly on the user's computer, as astand-alone software package, partly on the user's computer and partlyon a remote computer or entirely on the remote computer or server. Inthe latter scenario, the remote computer may be connected to the user'scomputer through any type of network, including a local area network(LAN) or a wide area network (WAN), or the connection may be made to anexternal computer (for example, through the Internet using an InternetService Provider). In some embodiments, electronic circuitry including,for example, programmable logic circuitry, field-programmable gatearrays (FPGA), or programmable logic arrays (PLA) may execute thecomputer readable program instructions by utilizing state information ofthe computer readable program instructions to personalize the electroniccircuitry, in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the blocks may occur out of theorder noted in the Figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

1. A computer usable program product comprising one or morecomputer-readable storage devices, and program instructions stored on atleast one of the one or more storage devices, the stored programinstructions comprising: program instructions to ionize a gas into aplasma; program instructions to mix a compound of a dopant into theplasma, forming a mixed plasma; program instructions to expose, using asemiconductor device fabrication system, a layer of III-V material tothe mixed plasma to dope the layer with the dopant up to a depth in thelayer, forming a shallow doped portion of the layer; programinstructions to control the depth of the dopant by a second layer of thedopant formed at the shallow doped portion of the layer; programinstructions to expose the second layer to a solution, the solutionprepared to erode the dopant in the second layer at a first rate; andprogram instructions to remove, after an elapsed period, the solutionfrom the second layer, wherein the elapsed period is insufficient toerode a total depth of the layer and the shallow doped portion by morethan a tolerance erosion amount.
 2. The computer usable program productof claim 1, further comprising: program instructions to compute, using aprocessor and a memory, the elapsed period as a function of thetemperature.
 3. The computer usable program product of claim 2, whereinthe function is an inverse relationship function.
 4. The computer usableprogram product of claim 1, wherein the computer usable code is storedin a computer readable storage device in a data processing system, andwherein the computer usable code is transferred over a network from aremote data processing system.
 5. The computer usable program product ofclaim 1, wherein the computer usable code is stored in a computerreadable storage device in a server data processing system, and whereinthe computer usable code is downloaded over a network to a remote dataprocessing system for use in a computer readable storage deviceassociated with the remote data processing system.
 6. The computerusable program product of claim 1, wherein the solution is heated to atemperature.
 7. The computer usable program product of claim 6, whereinthe temperature is in a range that includes sixty degrees Celsius. 8.The computer usable program product of claim 1, wherein the solutioncomprises Tetra Methyl Ammonium Hydroxide (TMAH) that has been dilutedto a ratio.
 9. The computer usable program product of claim 8, whereinthe ratio is a percentage range that includes twenty-five percent. 10.The computer usable program product of claim 1, further comprising:program instructions to adjust an amount of time the layer is exposed tothe mixed plasma to adjust an amount of the dopant in the second layer.11. The computer usable program product of claim 1, further comprising:program instructions to deposit, using the mixed plasma, the secondlayer of the dopant over the doped portion of the layer.
 12. Thecomputer usable program product of claim 1, further comprising: programinstructions to adjust an amount of the compound mixed into the plasmato adjust a speed of depositing the second layer.
 13. The computerusable program product of claim 1, wherein the shallow doped portionincreases an electron mobility in the layer up to a threshold level. 14.The computer usable program product of claim 1, further comprising:program instructions to remove, as a part of the exposing the layer tothe mixed plasma, oxygen from an oxide molecule in the layer, whereinthe removing the oxygen causes the dopant to reach the depth.
 15. Thecomputer usable program product of claim 1, wherein the dopant isSilicon, and wherein the compound is Silane.
 16. The computer usableprogram product of claim 1, wherein the gas is one of Argon and Helium.